New green surfactants for emulsion polymerization

Nonylphenol ethoxylates (NPEOs) are widely used as surfactants for emulsion polymerization and for post adding stabilization for latex applications in formulations with high filler content. However, the current exposure situation of NPEOs in Europe gives rise to environmental concern, despite of the fact that some industry associations have already pro-actively taken measures to phase out these chemistry of their products, e.g. the European detergent industry (AISE) by a voluntary commitment. As a consequence, the EU Commission has recommended to implement a risk reduction strategy, which foresees the ban of all applications leading to direct emissions to waste water and strict emission controls for all other technical processes using NPEOs as surfactant. The effectiveness of the risk reduction measures will be monitored by the authorities. In case that the environmental concentrations of NPEOs and their metabolites do not decrease by at least 70 percent, additional risk reduction measures for technical applications are planned. In one of the major fields of application, alkyl phenol-free emulsifiers with a more favorable ecological profile are becoming key ingredients for eco-friendly emulsion polymers and polymer dispersions: the Disponil^® AFX-Series (Cognis) is a NPEO-free surfactant system for emulsion polymerization and polymer dispersant also as a supposition for getting the European eco-label for indoor paints and varnishes.

These new non-ionic surfactant system exhibits an effective performance during polymerization and as post reaction stabilizers. These products are environmentally compatible, mostly derived from natural renewable resources and readily biodegradable. The underlying chemistry is in compliance with relevant indirect food contact applications [BfR recommendations, respectively, FDA CFR 21 (federal drug administration)], and a dossier to register the surfactants in the positive list of the EU Directive 2002/72/EC for application in plastic has recently been submitted.

Clear, high solid liquids at room temperature, these surfactants are easy to handle and very effective with regard to controlling particle size, film properties and overall latex stability. This paper summarizes their chemical and surface properties, as well as their performance in model emulsion polymerization formulations for architectural coatings.     

反应型表面活性剂对乳液聚合的影响

通过分析不同类型的反应型表面活性剂,包括可聚合乳化剂,表面活性引发剂和表面活性链转移剂的结构,讨论了其对乳液聚合的影响和在乳液聚合中的应用。     

Influence of steric length in electrosteric surfactants on emulsion polymerization

Four PPG Avanel Series S surfactants (sodium alkyl polyether sulfonates) with varying ethylene oxide content (n = 3, 7, 9, and 15) were used to investigate the influence of the steric length in this type of electrosteric stabilizers on emulsion polymerization. The polymerization studies employing potassium persulfate as an initiator with styrene, methyl methacrylate, and vinyl acetate monomers showed no apparent change in particle size, number of particles, and polymerization rate with the changing steric length of the surfactant. Steric influences were observed in the redox-initiated systems of styrene, butyl acrylate, and methyl methacrylate. Increasing the ethylene oxide unit content from three to nine units decreased the rate of polymerization, the particle size and number in the polystyrene latexes. Polymerizations with the acrylates displayed the same trend except that the polymerization rate reached a minimum value at nine ethylene oxide units and increased when the surfactant containing 15 ethylene oxide units was used.     

Preparation of epoxy acrylate emulsion using mixed surfactants and its polymerization

Summary A series of epoxy acrylate emulsions were prepared with several surfactants ranging from HLB 12 to 14 at 40°C. For epoxy acrylate emulsion, additives and conditions were established among factors: HLB value of emulsion, agitation speed, water dropping speed, and dropping amount of the deionized water. For emulsion polymereization with water soluble initiator KPS, emulsion was broken during polymerization, because interfacial complex formed by association of surfactant with co-surfactants stabilizing emulsion was weakened by interpenetration of radicals formed at aqueous. Accordingly, the polymerization of epoxy acrylate emulsion was carried out by using oil soluble initiator, AIBN, and the conversion changes with initiator concentration and HLB values were investigated.     

Using anionic polymerizable surfactants in ultrasonically irradiated emulsion polymerization to prepare polymer nanoparticles

An ionic polymerizable surfactant, sodium sulfopropyl‐laurylmaleate (M12), was synthesized and used as an emulsifier, an initiator, and a comonomer in ultrasonically irradiated emulsion polymerization. FTIR spectra and gravimetric method results indicated that copolymers P(Styrene‐M12) and P(Butylacrlate‐M12) were prepared successfully by ultrasonically irradiated emulsion polymerization and the composition of M12 elevated with the increasing concentration of M12 added. TEM photographs of P(St‐M12) showed that the nanoparticles with small diameters (20–45 nm) were prepared. With the increase of M12 concentration, the particle size became smaller and the size distribution became wider. The P(BA‐M12) particles size was also small (<100 nm) but the size distribution was wide due to the high reactivity of BA. Because surfmer M12 was chemically bonded with the latex particles, the stability of the copolymer latex prepared by ultrasonically irradiated emulsion polymerization was much better than that of the homopolymer latex (PSt or PBA) prepared by the same way. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Advances in emulsion polymerization for coatings applications: Latex blends and reactive surfactants

The utilization of latex blends to prepare zero-VOC coatings and the use of reactive surfactants in emulsion polymerization are two advances in waterborne technology that are of increasing interest to coatings formulators. The first part of this paper focuses on an investigation of the influence of the interface between high and low T_g latex particles on the gloss and surface morphologies offilms obtained from model latex blends. Gloss was influenced by the concentration of carboxyl groups present on the surface of the latex particles (optimal concentration for maximum gloss = 13% on the high T_g particles, the degree of neutralization of these groups (higher gloss with increased extent of neutralization), the type and concentration of the neutralizing base (higher gloss for stronger bases), and the presence of added surfactant (higher gloss with added surfactant). Gloss was found to be correlated with the surface smoothness of the film. The kinetics, partide size, molecular weight, and location of the reactive surfactant after polymerization, as well as the contact angle of films prepared from these latexes, are examined in the second part of this paper. The polymerization rate profiles were similar to those obtained using a conventional surfactant; however, the dependency of the rate on the number of particles was significantly lower. The amound bound increased and the molecular weight decreased with increasing surfactant concentration. Presented at the 78th Annual Meeting of the Federation of Societies for Coatings Technology, on October 16–20, 2000, in Chicago, IL. Emulsion Polymers Institute and Department of Chemical Engineering, 111 Research Dr., Bethlehem, PA, 18015-4791.     

含疏水侧链聚氨酯表面活性剂的制备及其乳液聚合应用研究

以异佛尔酮二异氰酸酯、二羟甲基丙酸和单硬脂酸甘油酯为主要原料,通过改变原料配比制备一系列含疏水侧链聚氨酯表面活性剂。采用FT-IR和~1H NMR对产物的结构进行了表征。以单体质量5%的聚氨酯表面活性剂制备了固含量(质量分数)为35%的聚甲基丙烯酸甲酯-co-聚丙烯酸丁酯乳液,研究了预聚物n(-NCO)/n(-OH)对表面活性和乳液聚合应用的影响。结果表明,当预聚物n(-NCO)/n(-OH)=1.07时,含疏水侧链聚氨酯表面活性剂水溶液具有最低表面张力值33.24 mN/m。该聚氨酯表面活性剂用于制备聚丙烯酸酯乳液可得到核壳结构乳胶粒子,当预聚物n(-NCO)/n(-OH)=1.11时,制备得到的乳胶粒子最小,直径约为75 nm。     

Reactive surfactants in heterophase polymerization

Summary Maleic, Styrenic and Methacrylic macromonomers of poly(ethylene oxide) and related polymerizable surfactants (SURFMERS) have been used as stabilizers in the dispersion polymerization of styrene in ethanol-water mixtures. The current study looks at the polymerization yield, the particle size and the incorporation yield of the stabilizers onto the surface of the particles. The macromonomers are better suited than the corresponding SURFMERS for steric stabilization of the particles.A series of publications from the EU program Human Capital and Mobility (CHRX CT 93-0159)     

Micellar polymerization of surfactants

Summary Micelle-forming sodium 6-acrylamidocaproate (Na 6-AAC) and sodium 11-(N-methyl acrylamido)undecanoate (Na 11-MAAU) were synthesized and polymerized in aqueous solutions. The polymerization was very rapid and it followed first-order kinetics with respect to the monomer and one-half order to K₂S₂O₈. The activation energy for the polymerization of Na 11-MAAU (62.3 kJ/mol) was much lower than that for Na 6-AAC (98.1 kJ/mol). The ¯M_w. for the former was around one million and it was only one-third of that for the latter. Their MWD (¯M_w/¯M_n - 1.5) are relatively narrow. The relationships between intrinsic viscosity []_o and ¯M_w for these polysurfactants have also been established.     

Crosslinking kinetics in emulsion polymerization

Network formation in free-radical polymerization is investigated both from experimental and theoretical points of view. In a bulk free-radical crosslinking copolymerization, the radical concentration increases significantly due to a decrease in the bimolecular termination rate. Some fraction of radicals is trapped during the course of network formation, and the reactivity of the radicals in liquid state is completely different from that in solid state (trapped radicals) in terms of both propagation and termination. In emulsion crosslinking polymerization, the crosslinking density tends to be fairly high even from the start of the polymerization. The crosslinking density development is substantially different from that in bulk and solution polymerizations, in which the crosslinking density increases with time, at least in the earlier stages of polymerization. Due to the elastic contribution of free energy change, the monomer concentration in the polymer particles is lower than for linear emulsion polymerizations as long as the monomer droplets exist, resulting in an enhanced tendency toward crosslinking reactions.     

Emulsification in batch emulsion polymerization

Dispersion of liquid–liquid systems is often applied in industrial processes such as extraction, suspension, and emulsion polymerization. The influence of emulsification of the monomer in the aqueous phase on the course and outcome of the batch emulsion polymerization of styrene has been studied. A visual criterion was applied for determining the lowest impeller speed for sufficient emulsification (N*). It appeared that in polymerization experiments under the same conditions, N* was the critical value above which no further increase in polymerization rate was observed. Using a turbine impeller instead of a pitched blade impeller as well as using a larger impeller diameter provides better emulsification at constant power input. The results indicate that scale‐up with constant impeller tip speed is most appropriate in case of a turbine impeller. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3225–3241, 1999     

Silicone-stabilized nonaqueous emulsion polymerization

Stable dispersions are prepared by free-radical polymerization of methyl methacrylate in aliphatic hydrocarbons containing poly(dimethylsiloxane) modified with mercaptoalkyl side groups. The particles are pictured as being stabilized by a protective layer of solvated poly(dimethylsiloxane). Some important features of the polymerization are described.     

乳液聚合方法研究进展

乳液聚合方法具有各方面的优点和广泛的应用范围,因此,受到人们的广泛关注。本文介绍了乳液聚合的优缺点,并着重介绍了一些新的乳液聚合方法及其原理、特点、应用以及中外最新的一些研究成果。     

Predominant droplet nucleation in emulsion polymerization

Emulsions stabilized against diffusional degradation by incorporating a polymeric cosurfactant have been produced and polymerized. The presence of large numbers of small droplets shifts the nucleation mechanism from micellar or homogeneous nucleation, to droplet nucleation. When an efficient cosurfactant is used, this process is referred to as miniemulsion polymerization. Polymer, however, is known to be a poor cosurfactant. Its advantage is that, unlike most cosurfactants, it is innocuous in the recipe. Results indicate that even a poor cosurfactant (polymer) is adequate to stabilize small droplets against diffusional degradation long enough to nucleate them into polymer particles. The dependence of the concentration and molecular weight of the cosurfactant on the droplet size and distribution is investigated. Droplet diameters range from 19.5 to 141.2 nm with polydispersities of about 1.023. The polymeric cosurfactant is found to affect the mechanism of nucleation. On-line conductance measurements are used to successfully differentiate between nucleation mechanisms. The observed reaction rates are dependent on the amount of polymeric cosurfactant present. In addition, the latexes prepared with the polymeric cosurfactant have lower polydispersities (1.006) than either latexes prepared from classical emulsions (1.049) or from alkane-stabilized miniemulsions (1.037). © 1996 John Wiley & Sons, Inc.     

无皂乳液聚合的最新研究进展

简单阐述了无皂乳液聚合的定义及其常见的聚合方法,介绍了无皂乳液聚合方法在活性可控自由基聚合(CRP)领域中的应用,对其在原子转移自由基聚合(ATRP)领域和在可逆加成-断裂链转移聚合(RAFT)领域的应用机理进行阐述.简要分析了提高乳液稳定性的方法,最后结合无皂乳液聚合技术的应用进展对其发展趋势做出展望.     

有机硅氧烷 -丙烯酸酯乳液聚合研究进展

介绍了有机硅-丙烯酸酯乳液聚合物的3种制备方法及各种乳液的特点,对各种乳液的近期研究成果进行了总结。     

种子乳液聚合制备MCPU-PMMA复合乳液

本文采用改性蓖麻油合成了软段中含不饱和双键的阴离子聚氨酯水分散液（MCPU），将其作为可聚合乳化剂和种子成分同甲基丙烯酸甲酯（MMA）进行共聚，制得了MCPU－PMMA复合乳液。1HNMR谱图显示MCPU中含有双键结构,共聚后双键消失。通过考察单体转化率和复合乳液平均粒径、凝胶量及成膜耐水及甲苯性探讨了影响种子乳液聚合的多种因素：采用过硫酸钾作为引发剂，单体转化率高，乳液粒径小，成膜耐水及甲苯性好；反应的表观活化能Ea为164.86kJ/mol，反应温度控制在70℃较适宜；聚合反应速率Rp∝［I］1.0856，引发剂用量宜控制在聚合有效组份总质量的0.5％。     

Radiation-induced emulsion polymerization of tetrafluoroethylene

The radiation-induced emulsion polymerization of tetrafluoroethylene was carried out with the use of ammonium perfluorooctanoate as an emulsifier at an initial pressure of ca. 30–35 Kg/cm². The polymerization rate was shown to be proportinal to about the 0.8 power of the dose rate in the range of 2 × 10⁴ to 10⁵ R/hr and to be almost independent of emulsifier concentration. The molecular weight of the polymer lies in the range of 10⁴ to 10⁵, increases with reaction time at the initial stage, and decreases with emulsifier concentration, but is independent of the dose rate from 2 × 10⁴ to 6 × 10⁴ R/hr. If the emulsifier is not used, a polymer with a molecular weight as high as 1.8 × 10⁶ to 2 × 10⁷ is obtained. Apparently, the emulsifier and its radiolysis products act as chain transfer agents. Postirradiation polymerization was found to take place with the formation of products with increased molecular weight.     

乳液聚合中的反应型乳化剂研究进展

介绍了反应型乳化剂的最近研究进展,并简述了其结构、分类和特点。探讨了可聚合乳化剂应用效果的几个影响因素和最佳可聚合乳化剂行为。对设计和使用可聚合乳化剂具有一定的指导作用。